Recently, fluorene derivatives such as 9,9-bis(4-(2-hydroxyethoxy)phenyl)fluorene and the like are promising as raw materials for producing polymers (for example, epoxy resins, polyesters, polyethers, polycarbonates and the like) excellent in heat resistance and transparency and having high refractive index, and expected as materials and raw materials of optical lenses, films, plastic optical fibers, optical disk platforms, heat resistant resins, engineering plastics and the like.
For producing thermally and optically excellent polymers in these applications, it is important that the molecular weight is high, the molecular weight distribution is narrow and the content of un-reacted monomers and oligomers is low, and it is desired that a raw material monomer 9,9-bis(4-(2-hydroxyethoxy)phenyl)fluorene is highly pure and excellent in reactivity. Thus, control of the purity of a raw material monomer, control of crystal form significantly influencing the reactivity and control of the melting point are important factors for obtaining a more excellent polymer. Further, for maintaining excellent performances in polymer production and carrying out more stable production, it is necessary to separately produce specific crystal forms capable of maintaining a constant quality.
As the method of producing 9,9-bis(4-(2-hydroxyethoxy)phenyl)fluorene, disclosed are a method of dehydration-condensing fluorenone and phenoxyethanol using sulfuric acid and thiols as catalysts (patent document 1) and a method of reacting 9,9-bis(4-hydroxyphenyl)fluorene and ethylene carbonate (non-patent document 1). We made an application of a novel production method (patent document 2) different from the above-described production method. Patent document 1 describes a method of purifying the compound according to the present invention and non-patent document 1 describes that the melting point of the compound according to the present invention is 126 to 128° C., however, there are until now known no information at all regarding maintenance of constant qualities, such as the presence of different crystal polymorphs of the compound, relation between different crystal polymorphs, methods of producing respective crystal polymorphs necessary for industrial operations, and the like.    (patent document 1) JP-A No. 7-165657    (patent document 2) JP-A No. 2007-23016    (non-patent document 1) Journal of Applied Polymer Science, 1995, Vol. 58, 1189-1197